Guess Paper XI Chemistry 2026 with complete solution

📘 Guess Paper XI Chemistry 2026

Prepared by Inam Jazbi – Learn Chemistry

• 🎯 Targeted Preparation: Covers key sections likely to appear in exams.
• 🔢 Important Numericals: Step-by-step solutions for scoring high marks.
• 🧪 Concept Clarity: Short-answer questions explained in simple language.
• ⏰ Smart Time Management: Suggested timings for each part to maximize efficiency.
• ✅ Exam-Oriented Approach: Structured exactly according to the paper pattern.

📝 Instructions

📚 Attempt 14 questions in all ---- 9 from Section B, 4 from Section C and the compulsory question No. 1 (Section A) of MCQs.

🔢 Write down proper numbering according to question paper. Do not copy questions.

✍️ Section B

🔹 Attempt 9 Short Questions ➡️ 4 marks each 🎯 Total = 36 marks

⏰ Suggested Time for Solution

🕒 Total: 90 mins

✍️ Each part: 9 mins

Q2 (i)

Define any 4 of the following:
Stoichiometry, Molar volume, Mole, Percentage yield, Exponential notation, Significant figure, Dipole moment, Tyndal effect, Anisotropy, Cleavage plane, Symmetry, Crystal growth, Transition temperature, Chemical equilibrium, Gay‑Lussac Law, Bond order, Debye, Unit cell, Bond energy, Colloid, Dispersion forces, Activation energy and Lattice energy, Rate expression, Rate constant, Critical temperature, Allotropy, Limiting reactant, Molar heat of vaporization, Dispersion force, Viscosity, Surface tension, Molar heat of fusion.

OR
Write down 2 differences between any TWO of the following:
➡️ Solution, colloids and suspension
➡️ Crystalline & amorphous solid
➡️ σ‑bond and π‑bond
➡️ Isomorphism and polymorphism
➡️ Ideal and non‑ideal solution
➡️ Polar and non‑polar bond
➡️ Continuous and line spectrum
➡️ Molecularity & reaction order
➡️ Lyman and Balmer series
➡️ VBT and MOT
➡️ Hydrophobic and Hydrophilic molecules
➡️ Positive and negative catalyst
➡️ BMO and AMO

Q2 (ii)

State Hund’s rule of multiplicity, Aufbau principle and Pauli exclusion principle. Write the values of four quantum numbers for the valence electrons of He and Mg (Z = 12). Also write down the electronic configuration for ground states of each of the following:
Zn, S²⁻, Cr (24), Cu (29), Fe³⁺ (26), Br⁻ (35), Mo (42), Ag (Z = 47), Pd (Z = 46), Ca²⁺ (Z = 20), Cl⁻, Sr²⁺ (38)

OR
What is meant by dipole moment? Give its mathematical formulae and different units. On what factors does it depend? Which of the following molecules have dipole moment? In each case, give a reason for your answer: CO₂, CHCl₃, SCl₂, H₂O, CCl₄

Q2 (iii)

What are quantum numbers and orbitals? Give a brief account of 4 quantum numbers. Write all possible values of l, m and s for n = 2 and n = 3. Draw the shape of different orbitals with l = 2. Arrange the following orbitals according to Wiswesser rule: 4f, 3d, 4s, 6p, 7s, 5d.

OR
What is bond energy? Give applications. What are the various parameters which correlate bond energy with bond strength?

Q2 (iv)

Write Limitations of Bohr’s theory. Which rule and principle is violated in writing the following E.C.:
➡️ 1s², 2s³ (Pauli’s exclusion principle; correct: 1s², 2s² 2pₓ¹)
➡️ 1s², 2pₓ² (Aufbau principle; correct: 1s², 2s²)
➡️ 1s², 2s², 2pₓ² 2pᵧ¹ (Hund’s rule; correct: 1s², 2s² 2pₓ¹ 2pᵧ¹ 2p_z¹)
➡️ 1s², 2s² 2p⁶, 3s² 3p⁶, 3d⁴ 4s³ (Pauli’s exclusion principle and Hund’s rule; correct: [Ar], 3d⁵ 4s¹)

Q2 (v)

What is Hybridization? Give three differences between three types of hybridization. Draw the shape of ethene and ethyne molecules on the basis of Hybridization.

OR
Draw dot and cross structures of O₂, N₂, CH₄, CO₂, CHCl₃, C₂H₂, C₂H₄. Explain the ionic character of covalent bond.

(vi)

What are X-rays? How are they produced? Give their types and uses. What is the Relationship between Wavelength of X-rays and Nuclear Charge of Atom & how did Atomic Number discover by Moseley (role of X-rays in Moseley’s contribution)?

OR
Describe strength of covalent bond in term of VBT. Write down limitations of VBT.

(vii)

Define the process of hydrolysis. Explain the behavior of each of the following salts in aqueous solution with equations:
(a) K₂CO₃    (b) (NH₄)₂SO₄    (c) NaNO₃

OR
Define buffer, buffer action and buffer capacity? Explain the mechanism of buffer action with its applications.

(viii)

What do you mean by solubility product? Derive an expression for K_sp. Write down the solubility product expressions for the following sparingly soluble salts along with their units:
(i) Mg(OH)₂    (ii) Mg₃(PO₄)₂

What is meant by reaction rate? Enlist various factors which influence the rate of chemical reactions and describe the effect of temperature and surface area of solid reactant on reaction rate.

(ix)

What are the units for the rate constants for zero order, 1st order, 2nd order and 3rd order reactions?

OR
Differentiate between Elementary and Complex Reactions. What is reaction mechanism? Explain it with the help of example.

OR
Differentiate between homogeneous and heterogeneous catalysis. Give one example of each.

(x)

Define three major kinds of intermolecular forces in liquids. Explain intermolecular forces in HCl.

OR
What is London force? How is it originated? Describe factors on which strength of these forces depend.

OR
What is hydrogen bond? How is it established? Give its applications in industrial and biochemical processes. Describe hydrogen bonding in water and explain high specific heat, and the anomalous behaviour of water due to hydrogen bonding.

(xi)

What is oxidation number? State its any seven rules with examples. Find the oxidation number of the following (Write only value of oxidation numbers):
➡️ N in NH₄NO₃    ➡️ P in K₂MgP₄O₇ and Ca(H₂PO₄)₂    ➡️ S in Na₂S₄O₆ and Na₂S₂O₃
➡️ Ni in Ni(CO)₄    ➡️ Cr in Cr₂O₇²⁻ and H₂CrO₄    ➡️ Fe in Fe(CO)₃ and Fe₃O₄
➡️ Mn in MnO₄⁻    ➡️ C in CNO⁻ and C₃O₄    ➡️ P in POCl₃
➡️ Cl in CaOCl₂    ➡️ Cl in HOCl and HClO₄    ➡️ Br in BrO₃⁻

OR
What is meant by electrolysis? Explain the electrolysis of molten CaCl₂.

OR
Draw a fully labeled Born Haber cycle for Rubidium chloride (RbCl) and determine the lattice energy by using the following values (all in kJ/mol). (Answer: −692 kJ/mol)
➡️ I.P1st of Rb = 403 kJ/mol
➡️ Electron affinity of Cl = −349 kJ/mol
➡️ Bond energy of Cl₂ = 242 kJ/mol
➡️ Sublimation energy of Rb = 86.5 kJ/mol
➡️ Heat of formation of RbCl = −430.5 kJ/mol

(xii)

What are Colloids? Define their two types based on water as dispersion medium or physical state. Write down their Properties.

OR
What is liquid crystal? Give its two properties and two uses.

(xiii)

Define four types of solids according to bonding. Describe any two of them.

OR
Define lattice energy. Explain how it is affected by size and charge of ion?

OR
Define unit cell. How can you determine the number of Na⁺ and Cl⁻ ions in one unit cell of sodium chloride (NaCl)?

(xiv)

Define surface tension and viscosity with their units. Describe the two factors that affect them.

OR
What is the fourth state of matter? Give its significance in daily life.

(xv)

What is corrosion? What causes it to form? What can be done to prevent its formation?

(xvi)

State and explain Hess’s law of constant enthalpy summation. Calculate the enthalpy of combustion of propane at 25°C by the given information:
C₃H₈(g) + 5O₂(g) → 3CO₂(g) + 4H₂O(g)    ∆H° = ?
∆Hf° of C₃H₈(g) = −103.9 kJ/mol
∆Hf° of CO₂(g) = −393.5 kJ/mol
∆Hf° of H₂O(g) = −285.8 kJ/mol

(xvii)

What are colligative properties? Why does the boiling point of a liquid get raised when a non‑volatile solute is added? Explain depression in freezing point of dilute solution.

OR
Define oxide and salt. Explain three types of oxides and four types of salts based on their acid‑base properties with examples.

(xviii)

Define Electrode potential and SHE. How is electrode potential of Zinc or Cu determined?

OR
What is battery? Define primary and secondary batteries. Describe the construction and working of lead storage battery with the help of relevant chemical equations or dry cell.

(xix)

Give Scientific reactions of any 4 of the following:
➡️ CO₂ is non‑polar while H₂O (or SO₂) is Polar molecule.
➡️ The boiling point of water is greater than that of HF even though F has greater EN than O.
➡️ s‑s sigma bond is weaker than s‑p or p‑p sigma bond.
➡️ 100 cm³ of O₂ and 100 cm³ of NH₃ contain the same number of molecules at STP.
➡️ The rates of diffusion of CO₂ and C₃H₈ gases are the same.
➡️ Evaporation is a cooling process.
➡️ Density of water is highest at 4°C.
➡️ Glycerin is distilled at reduced pressure.
➡️ H₂O forms concave meniscus while Hg forms convex meniscus.
➡️ Ethyl alcohol (C₂H₅OH) has greater viscosity than diethyl ether (C₂H₅OC₂H₅).
➡️ Powdered zinc or marble (CaCO₃) reacts quickly with hydrochloric acid than its solid lump.
➡️ Milk sours more rapidly in summer than in winter.
➡️ Why n‑hexane (petrol) is immiscible in water?
➡️ Pressure cooker is used for rapid cooking.
➡️ Vapour pressure of solution is lowered by adding non‑volatile solute.
➡️ A free falling drop of liquid is spherical.
➡️ Sigma bond is stronger than pi bond.
➡️ All photochemical reactions are zero order reactions.
➡️ Aqueous solution of Na₂CO₃ is alkaline while aqueous solution of NH₄Cl is acidic in nature.
➡️ Vapour pressure of solution is lowered by adding non‑volatile solute.
➡️ Solubility of oxygen in water increases with pressure but solubility of glucose in water has negligible effect of pressure.

(xx)

Do as directed (any 4 of the following):
➡️ Calculate wave number of an electron when it jumps from orbit 5 to orbit 2.
➡️ Arrange the following energy levels in ascending order using (n+l) rule: 5d, 3s, 4f, 7s, 6p, 2p
➡️ Define an electrochemical series? Give its properties.
➡️ Sketch a zinc‑copper Galvanic cell.
➡️ Define pH and pOH of a solution. Also show that pH + pOH = 14.
➡️ A solution is made by dissolving 14.8 g HCl in water at 25°C. If the volume of solution is 750 cm³ and HCl is assumed to be completely ionized, calculate its pH.
➡️ Calculate the molar mass of an unknown gas whose effusion rate is 2.83 times the effusion of methane.
➡️ The threshold energy of a reaction is 30 J. The average internal energy is 19 J. Calculate Ea.
➡️ Calculate the number of molecules and the volume in cm³ at STP of 0.28 g of nitrogen gas.
➡️ Calculate the density of oxygen gas at 45°C when the gas is confined in cylinder at 1170 torr pressure.
➡️ A cylinder contains 2.2 moles of oxygen gas at STP. When more oxygen gas is pumped into the cylinder, the volume of gas is changed from 2.0 dm³ to 3.4 dm³. Calculate how many moles of the oxygen gas are added to the cylinder? [Answer: n₂ = 3.74, moles added = 1.54 moles]
➡️ 150 cm³ of H₂ gas was collected over water at 800 mm Hg and 28°C. Calculate the mass in gram of H₂ gas obtained. The pressure of water vapours at 28°C is 20 mm Hg.
➡️ 40 g of NH₃ is confined in a vessel at STP. Find number of moles, number of molecules, volume of NH₃ gas and number of hydrogen atoms.

✍️ Section C

🔹 Attempt 4 Long Questions ➡️ 8 marks each 🎯 Total = 32 marks

⏰ Suggested Time for Solution

🕒 Total: 70 mins

✍️ Each part: 16 mins

Q3.

State the postulates of Bohr’s atomic theory with its defects? Derive an expression for the frequency and wave number expression of photon from E = −k (1/n²) or energy of nth stationary state of hydrogen atom?

OR
What are Rate Law and Rate Constant. Derive rate expression for a general chemical reaction. Enlist various factors which influence on the rate of chemical reactions and describe the effect of concentration of reactants, surface area and temperature on the reaction rate.

Q4.

State and explain first law of thermodynamics. Prove that:
(i) ∆H = q_p by deriving Pressure volume work
(ii) ∆E = q_v. Draw diagram where necessary.

OR
State the basic postulates of Kinetic Molecular Theory. State and explain Avogadro’s law or Charles law.

Q5.

State the basic postulates of VSEPR theory. Predict the geometry of molecules containing the following electron pairs on their central atom:
➡️ Three bond pairs and one lone pair (NH₃ or PH₃ or PCl₃)
➡️ Two bond pairs and two lone pairs (H₂O or H₂S or OF₂)
➡️ Three bond pairs and no lone pairs (AlCl₃ or BF₃)
➡️ Two bond pairs and no lone pair (CO₂ or CS₂)
➡️ Two bond pairs and one lone pair (SO₂)

OR
Explain the shapes of any three of the following molecules on the basis of hybridization and electron pair repulsion theory: Ethene, Ethyne, CH₄, H₂O, NH₃

OR
State the postulates of Molecular Orbital Theory. Draw the MO diagram of O₂/N₂ molecule. Find:
(i) Molecular orbital configuration
(ii) Bond order
(iii) Magnetic nature

Q6.

What are the conditions of deviation of real gas from ideal behaviour? Write down Graphical Explanation of Deviation of Real Gases. Derive van der Waal’s equation for real gases by correcting volume and pressure. Deduce Units for van der Waal’s Constants ‘a’ and ‘b’.

OR
Differentiate between ideal and non‑ideal gas. What are the conditions of deviation of real gas from ideal behaviour? Write down Graphical Explanation of Deviation of Real Gases. Discuss the deviation of Ideal behaviour of gases at low temperature and high pressure.

OR
Derive ideal gas equation by combining the gas laws. Calculate SI value and calorific value of molar gas constant.

Q7.

State and explain law of equilibrium. How can we predict the direction of reversible reaction with the help of reaction quotient? Derive K_c expression using this law for a general reaction and following reversible reaction: mN₂ + nH₂ ⇌ xNH₃.

State and explain Graham’s law or Dalton’s law of partial pressure with its applications.

Q8.

State Lewis concept or Bronsted‑Lowry concept of acids and bases with examples. Also explain conjugate acid‑base pair. Write equation and indicate the conjugate acid‑base pairs for the following:
(i) Acetic acid and ammonia
(ii) Hydrochloric acid and water
(iii) Ammonia and water

Q9.

State Le‑Chatelier’s Principle. Describe the effect of change in concentration and change in pressure on Equilibrium. Explain the industrial application of Le‑Chatelier’s principle using Haber’s process.

Predict the effect of increase in temperature and pressure on the following systems at equilibrium state (only predict the direction):
(i) 2SO₂(g) + O₂(g) ⇌ 2SO₃(g) + Heat
(ii) N₂(g) + O₂(g) + Heat ⇌ 2NO(g)

Q10.

State Raoult’s law. Derive this law mathematically in three forms. Under what conditions does Raoult’s law apply?

OR
Define osmosis and semipermeable membrane. Explain that osmosis is a colligative property of solution. Give four daily life examples of osmosis.

Q11.

What is redox reaction? Balance any two of the following equations by ion‑electron method (No description is required):
➡️ Cr(OH)₃ + H₂O₂ → CrO₄²⁻ + OH⁻ (basic medium)
➡️ Cl₂ + OH⁻ → Cl⁻ + ClO₃⁻ + H₂O (basic medium)
➡️ H₂S + HNO₃ → S + NO + H₂O (acidic medium)
➡️ MnO₄⁻ + SO₃²⁻ → MnO₂ + SO₄²⁻ (acidic medium)

✨📊 Key Numericals 🔢 🎯

🌟 Chapter # 1
Q1.

How many gram of NH₃ are formed when 100 g of each of the following reagents are reacted together according to following equation:
2NH₄Cl + Ca(OH)₂ → CaCl₂ + 2NH₃ + 2H₂O
(Answer; 31.773 g NH₃)

OR
How many grams of sodium thiosulphate (Na₂S₂O₃) will be produced when 200 g of each of Na₂S, Na₂CO₃ and SO₂ are reacted together.
2Na₂S + Na₂CO₃ + 4SO₂ → 3Na₂S₂O₃ + CO₂
(Answer; 369.72 g Na₂S₂O₃)

OR
Hydrogen gas is commercially prepared by steam methane process:
CH₄ + H₂O → CO + 3H₂
If a mixture of 28.8 g methane and 14.4 g steam is heated in a furnace at elevated temperature to liberate carbon monoxide and hydrogen gas, determine the limiting reactant and the mass and volume of hydrogen gas produced.
(Answer; H₂O is LR, mole of H₂ = 2.4 mole, Mass of H₂ = 4.8 g, Volume of H₂ = 53.76 dm³)

OR
60 g of hydrogen sulphide (H₂S) burns with 40 g oxygen (O₂) according to the equation:
2H₂S + 3O₂ → 2SO₂ + 2H₂O
Calculate the mass in gram and volume of SO₂ gas at STP.
(Answer; 60 g SO₂, Volume = 42 L at STP)

OR
Under high pressure magnesium (Mg) reacts with oxygen (O₂) to form magnesium oxide (MgO).
2Mg + O₂ → 2MgO
If 4 g of Mg reacts with excess of O₂ to produce 4.24 g of MgO, calculate the percentage yield of MgO.
(Answer; 63.85%)

OR
6.8 g of Mg reacts under high pressure with excess of O₂ to produce 10.44 g of MgO. Calculate the percentage yield of MgO.
2Mg + O₂ → 2MgO
(Answer; 95.6%)

Q2.

Aluminium Sulphide is prepared by the reaction of aluminium metal and sulphur powder at elevated temperature:
2Al + 3S → Al₂S₃
If 135 g aluminium and 160 g sulphur are taken for the reaction, calculate what mass of Al₂S₃ will be formed. If 155 g of Al₂S₃ is obtained then find out the % yield of this reaction.
(Answer; Theoretical yield = 222.2 g Al₂S₃, % yield = 69.8%)

OR
When aluminium is heated with nitrogen at 700°C, it gives aluminium nitride:
2Al(s) + N₂(g) → 2AlN(s)
If 67.5 g of aluminium and 140 g of nitrogen gas are allowed to react, find out:
(a) Limiting reactant and Mass of aluminum nitride produced?
(b) Mass of excess reactant?
(Answer; Al is LR, 102.5 g AlN produced, 105 g N₂ left behind)

🌟 Chapter # 2

Q3.*

A photon of wave number 23 × 10⁵ m⁻¹ is emitted when electron undergoes a transition from a higher orbit to n = 2. Determine the orbit from which electron falls and also the spectral line appears in this transition of electron (The value of Rydberg constant is 1.09678 × 10⁷ m⁻¹).
[Ans; n₂ = 5.05 ≈ 5, Number of spectral lines = 6]

🌟 Chapter # 4

Q4.

Four containers of equal volume are filled as follows: [Hint: Suppose Volume = 1 dm³].
(i) 2.0 g of H₂ at 0°C    (ii) 1.0 g of H₂ at 273°C
(iii) 24 g of O₂ at 0°C    (iv) 16 g of CH₄ at 273°C
(a) Which container is at the greatest pressure?
(b) Which container is at the lowest pressure?
[Answer; Container (iv) is at highest pressure, Container (iii) is at lowest pressure]
(Ans: P₁ = 22.4 atm; P₂ = 22.4 atm; P₃ = 16.8 atm; P₄ = 44.8 atm)

Q5.

40 dm³ of hydrogen gas was collected over water at 831 torr pressure at 23°C. What would be the volume of dry hydrogen gas at standard conditions? The vapour pressure of water at 23°C is 21 torr of Hg.
[Answer; V₂ = 39.32 dm³]

Q6.

A 500 cm³ vessel contains H₂ gas at 400 torr pressure and another 1 dm³ vessel contains O₂ gas at 600 torr pressure. If under the similar condition of temperature these gases are transferred to 2 dm³ empty vessel, calculate the pressure of the mixture of gases in new vessel.
[Answer; P_T = 100 + 300 = 400 torr]

Q7.

Two moles of oxygen gas is kept in a vessel of 15.5 dm³ at a temperature of 37°C. Calculate the pressure exerted by the gas if:
(a) gas behaves as ideal
(b) gas behaves as non‑ideal
a = 1.36 atm dm⁶ mol⁻² and b = 0.0318 dm³ mol⁻¹.
[Answer; P_ideal = 3.28 atm, P_real = 3.27 atm]

Q8.

At a specific temperature and pressure, it takes 290 s for a 1.5 dm³ sample of He to effuse through a porous membrane. Under similar conditions, if 1.5 dm³ of an unknown gas “X” takes 1085 s to effuse, calculate the molar mass of gas “X”.
[M_x = 55.96 ≈ 56 g/mol]

Q9.

If it takes 8.5 seconds for 5 cm³ of CO₂ gas to effuse through a porous material at a particular temperature and pressure. How long would it take for 5 cm³ of SO₂ gas to effuse from the same container at the same temperature and pressure?
[Answer; 10.43 seconds]

Q10.

Oxygen gas is produced by heating potassium nitrate:
2KNO₃ → 2KNO₂ + O₂
The gas is collected over water. If 225 cm³ of gas is collected at 25°C and 785 mm Hg total pressure, what is the mass of O₂ gas collected? (Pressure of vapours at 25°C is 23.8 mm Hg)
[Answer; n_O₂ = 9.2 × 10⁻³ mole, Mass = 0.294 g O₂]

Q11.

A chemist has synthesized a gas whose density was found to be 1.88 g dm⁻³ at 27°C and 760 torr pressure. Calculate its molar mass.
[Answer; M = 46.0 g/mol]

Q12.

The volume of hydrogen gas collected over at 24°C and 762 mmHg pressure is 1280 cm³. Calculate mass of hydrogen gas in gram obtained. The aqueous tension of water at 24°C is 22 mmHg.
The rate of diffusion of an unknown gas is 70.3 cm³/s whereas CO₂ is 60 cm³/s under similar conditions. What is the molecular mass and identity of the unknown gas?
[Answer; Mass of H₂ = 0.101 g; Molar mass of unknown gas ≈ 44 g/mol, Identity = CO₂]

🌟 Chapter # 7

Q1.

Following reaction was studied at 25°C:
2NO(g) + Cl₂(g) ⇌ 2NOCl(g)
At equilibrium, the partial pressures are:
P_NOCl = 1.2 atm,
P_NO = 5 × 10⁻² atm,
P_Cl₂ = 3 × 10⁻¹ atm.
Calculate the values of K_p and K_c.
[Answer; K_p = 1.92 × 10³ atm⁻¹, K_c = 1.89 × 10³ mol⁻¹ dm³]

Q2.

Nitrosyl chloride is a yellow coloured gas prepared by the reaction of NO and Cl₂ gases:
2NO(g) + Cl₂(g) ⇌ 2NOCl(g)
If at certain temperature, the partial pressure of equilibrium mixture is:
NO = 0.17 atm, Cl₂ = 0.2 atm and NOCl = 1.4 atm, calculate K_p.
(Answer; 339.1 atm⁻¹)

Q14.

Ethyl acetate is an ester of ethanol and acetic acid commonly used as an organic solvent:
CH₃COOH(l) + C₂H₅OH(l) ⇌ CH₃COOC₂H₅(l) + H₂O(l)
In an esterification process, 180 g of acetic acid and 138 g of ethanol were mixed at 298K and allowed to start reaction under necessary conditions. After equilibrium is established, 60 g of unused acid were present in the reaction mixture. Calculate K_c.
(Answer; 4)

OR
At 444°C reaction of hydrogen and iodine is performed in a sealed 1 dm³ steel vessel:
H₂(g) + I₂(g) ⇌ 2HI(g)
If equilibrium mixture contains 1 mole of H₂, 1 mole of I₂ and 7 moles of HI, calculate:
(a) Equilibrium constant (K_c)
(b) Initial concentration of H₂ and I₂
(Answer; [H₂]ᵢₙᵢₜᵢₐₗ = 4.5 mol/dm³, [I₂]ᵢₙᵢₜᵢₐₗ = 4.5 mol/dm³)

🌟 Chapter # 7 (continued)

Q8.

Calculate the value of Kₚ for the given reaction:
N₂ + 3H₂ ⇌ 2NH₃ at 27°C if the value of Kᴄ is 0.0012 mol⁻² dm⁶. (R = 0.0821 atm·dm³·mol⁻¹·K⁻¹)
[Answer; Kₚ = 2.99 × 10⁻⁵ atm⁻²]

Q9.

The reaction of methane with hydrogen sulphide gives carbon disulphide:
CH₄(g) + 2H₂S(g) ⇌ CS₂(g) + 4H₂(g)
If Kc for this reaction at 727°C is 4.2 × 10⁻³, calculate its Kₚ.
(Answer; 28.30)

Q10.

Kc for the given reaction at certain temperature is 2.72:
A(g) + 3B(g) ⇌ 2C(g)
If in a 5 dm³ vessel the reaction mixture contains 8 moles A, 6 moles B and 5 moles C. Predict whether the reaction is in equilibrium, if not what is the direction of net reaction.
(Answer; Q = 0.36 dm³ mol⁻¹, Forward Reaction)

Q11.

164 g H₂ and 518.4 g I₂ are mixed and reacted in a sealed 1 dm³ steel vessel at 444°C until the equilibrium is established, 338 g of HI is formed. Calculate Kᴄ.
H₂ + I₂ ⇌ 2HI
[Answer; Kᴄ ≈ 49]

Q12.

A solution is prepared by mixing 600 cm³ of 7.5 × 10⁻⁴ M BaCl₂ into 300 cm³ of 2.4 × 10⁻³ M Na₂SO₄ solutions. Will precipitate of BaSO₄ form when equilibrium is reached? (Kₛₚ of BaSO₄ = 1.1 × 10⁻¹⁰ mol² dm⁻⁶)
[Answer; Q = 3.6 × 10⁻⁷ > Kₛₚ, Precipitate forms]

Q13.

The solubility of AgCl at 25°C is 1.4 × 10⁻³ g/dm³. Its molecular mass is 143.5. Calculate molarity of AgCl solution and solubility product of AgCl.
(Kₛₚ = 9.5 × 10⁻¹¹ M²)

Q14.

Find the solubility of MgF₂ when its Kₛₚ is 7.26 × 10⁻⁹ mol³/dm⁹.
(x = 1.219 × 10⁻³ mol/dm³, Solubility of MgF₂ = 7.55 × 10⁻² g/dm³)

Q15.

Should AgCl precipitate from a solution prepared by mixing 400 cm³ of 0.1 M NaCl and 600 cm³ of 0.03 M AgNO₃. Kₛₚ of AgCl is 1.6 × 10⁻¹⁰ mol²/dm³.
(Q = 7.2 × 10⁻⁴ M², AgCl should form ppt)

🌟 Chapter # 9

Q1.

Decomposition of NO₂ into NO and O₂ is of second order reaction:
2NO₂ → 2NO + O₂
If the rate constant at certain temperature is 3.8 × 10⁻⁴ dm³ mol⁻¹ s⁻¹ and the initial concentration of NO₂ is 0.38 M, calculate the initial rate of reaction.
[Answer; Rate = k[NO₂]² = 3.8 × 10⁻⁴ × (0.38)² = 5.49 × 10⁻⁵ mol dm⁻³ s⁻¹]

Q2.

The rate constant for the decomposition of NOCl is 2.48 × 10⁻² dm³ mol⁻¹ s⁻¹. Calculate the initial rate when initial concentration of reactant is 0.65 mol/dm³. What will happen to the rate of reaction and rate constant, if the concentration of NOCl is doubled?
2NOCl → 2NO + Cl₂
[Answer; Rate = k[NOCl]² = 2.48 × 10⁻² × (0.65)² = 0.0105 mol dm⁻³ s⁻¹. If [NOCl] is doubled, rate becomes 4× (0.042 mol dm⁻³ s⁻¹), but k remains constant.]

Q3.

The rate constant (k) for the decomposition of NO₂ is 1.8 × 10⁻³ dm³ mol⁻¹ s⁻¹.
2NO₂ → 2NO + O₂
Write the rate expression.
Find the initial rate when the initial concentration of NO₂ is 0.75 mol dm⁻³.
Find the value of the rate constant when the initial concentration of NO₂ is doubled.
[Answer; Rate expression: Rate = k[NO₂]². Initial rate = 1.8 × 10⁻³ × (0.75)² = 1.01 × 10⁻³ mol dm⁻³ s⁻¹. If [NO₂] is doubled (1.5 M), rate = 1.8 × 10⁻³ × (1.5)² = 4.05 × 10⁻³ mol dm⁻³ s⁻¹. Rate constant k remains unchanged = 1.8 × 10⁻³ dm³ mol⁻¹ s⁻¹.]

🌟 Chapter # 9

Q3.

The initial rate data in a series of experiments while working on the hydrolysis of ester into acetic acid and ethyl alcohol is given in the following table. Determine its rate law, order of reaction and rate constant along with unit.
CH₃COOC₂H₅ + H₂O → CH₃COOH + C₂H₅OH

Experiment #	Initial [CH₃COOC₂H₅]; M	Initial [H₂O]; M	Initial rate; M s⁻¹
1	0.1	0.1	4 × 10⁻⁴
2	0.4	0.1	1.6 × 10⁻³
3	0.1	0.4	4 × 10⁻⁴

[Answer; Rate law = k[CH₃COOC₂H₅]¹, Order = 1, k = 4 × 10⁻³ s⁻¹]

OR

The initial rate data in a series of experiments while working on the oxidation of nitric oxide to give nitrogen dioxide is given in the following table. Determine its rate law and find the order of reaction.
2NO + O₂ → 2NO₂

Experiment #	Initial [NO]; M	Initial [O₂]; M	Initial rate; M s⁻¹
1	0.10	0.10	8 × 10⁻⁴
2	0.10	0.20	16 × 10⁻⁴
3	0.20	0.10	16 × 10⁻⁴

[Answer; Rate law = k[NO]²[O₂]¹, Order = 3]

OR

Determine the order of reaction and rate constant by the given data:

Initial [A]; mol dm⁻³	Initial [B]; mol dm⁻³	Initial rate; mol dm⁻³ s⁻¹
0.1	0.1	2.52 × 10⁻³
0.2	0.1	10.08 × 10⁻³
0.1	0.2	5.04 × 10⁻³

[Answer; Rate law = k[A]²[B]¹, Order = 3, k ≈ 0.252 dm⁶ mol⁻² s⁻¹]

OR

The experimental data for the kinetic study of a reaction; A + B → C, at 80°C is given below:

Determine the order of reaction and rate constant by the given data:

Experiment #	Initial [A]; mol dm⁻³	Initial [B]; mol dm⁻³	Initial rate of C; mol dm⁻³ s⁻¹
1	0.1	0.05	1.25 × 10⁻⁴
2	0.2	0.05	2.5 × 10⁻⁴
3	0.1	0.1	5.0 × 10⁻⁴

[Answer; Rate law = k[A]¹[B]², Order = 3, k ≈ 0.025 dm⁶ mol⁻² s⁻¹]

🌟 Chapter # 10

Q1.

Glucose is a non-volatile solute in water. A glucose solution contains 0.15 moles glucose and 5.8 moles water at 20°C. Determine the lowering in the vapour pressure if the vapour pressure of pure water at 20°C is 17.5 torr. (Assume solution is an ideal).
(Answer; ∆P = P° X₂ = 17.5 × 0.0252 = 0.441 torr)

Q2.

Calculate the molality of a 12% urea solution (molar mass of urea is 60 g/mol).
(Answer; 2.27 mol/kg)

Q3.

Define molality of solution. Calculate the molality of 25% (w/w) aqueous solution of glucose (molar mass of glucose is 180 g/mol).
(Answer; Molality = 1.39 mol/kg)

Q4.

An aqueous solution of 1.2 molality is prepared by dissolving some amount of oxalic acid into 475 g water. Determine the mass of oxalic acid in the solution. (Molecular mass of oxalic acid is 126 g/mol).
(Answer; 71.82 g)

Q5.

45 g glucose dissolves in 72 g water to make a solution. Calculate the mole fraction of glucose and water in the solution.
(Answer; 0.0588, 0.941)

Q6.

In the analysis of water sample, it was reported that 1 g of water contains 6.34 × 10⁻³ mg magnesium ions. Calculate the concentration of magnesium ion in ppm.
(Answer; 6.34)

Q7.

Automotive antifreeze is a 60% aqueous solution of ethylene glycol (C₂H₆O₂). Determine:
(a) molality of solution
(b) mole fraction of ethylene glycol in the solution
(Answer; molality = 24.19 mol/kg, mole fraction of ethylene glycol = 0.3, mole fraction of water = 0.693)

Q8.

The vapour pressure of a pure liquid A is 37 mm Hg at 27°C. It is mixed into another liquid B to make a solution. The vapour pressure of A in the solution is found to be 33 mm Hg. Calculate the mole fraction of A (Assume it obeys Raoult’s law).
(Answer; 0.441)

🌟 Chapter # 11

Q1.

Calculate the standard enthalpy of formation of Glycerol from the data given below.
➡️ 3C₍ₛ₎ + 4H₂₍g₎ + 3/2O₂ → C₃H₈O₃₍ₗ₎ ΔHf° = ?
➡️ C₍ₛ₎ + O₂₍g₎ → CO₂₍g₎ ΔH° = −393.5 kJ/mol
➡️ H₂(g) + ½O₂₍g₎ → H₂O₍ₗ₎ ΔH° = −285.8 kJ/mol
➡️ C₃H₈O₃₍ₗ₎ + 3½O₂(g) → 3CO₂(g) + 4H₂O(l) ΔH° = −1654.1 kJ/mol
[Answer; ΔHf°(C₃H₈O₃) = −669.5 kJ/mol]

Q2.

Calculate the heat of formation of ethane at 25°C from the following data:
➡️ 2C₍ₛ₎ + 3H₂₍g₎ → C₂H₆₍g₎ ΔHf° = ?
➡️ C₍ₛ₎ + O₂₍g₎ → CO₂₍g₎ ΔH = −394 kJ/mol
➡️ H₂₍g₎ + ½O₂₍g₎ → H₂O₍g₎ ΔH = −286 kJ/mol
➡️ C₂H₆ + 7/2 O₂₍g₎ → 2CO₂₍g₎ + 3H₂O₍g₎ ΔH = −1561 kJ/mol
[Answer; ΔHf°(C₂H₆) = −84 kJ/mol]

Q3.

A thermochemical process is carried out at constant pressure of 8.52 atm. If it absorbs 15.5 kJ energy from the surrounding, due to which an expansion in the volume of 4.7 dm³ is occurred. Calculate its change in internal energy.
[Answer; ΔE = q − PΔV = 15.5 − (8.52 × 4.7 × 0.1013) = 11.44 kJ]

OR
A thermochemical process is carried out at constant pressure of 2759 N/m². If it absorbs 15400 J heat energy from the surrounding due to which volume increases by 0.47 m³ by pushing the piston upward. Calculate the change in internal energy in kJ.
[Answer; ΔE = 15400 − (2759 × 0.47) = 14100 J ≈ 14.1 kJ]